In recent years, generation of carbon dioxide accompanying burning of fossil fuels is acknowledged as a problem. Therefore, utilization of natural energy, such as solar thermal energy, wind energy, hydro-energy and the like, is promoted. Among the natural energy, wind energy and hydro-energy are kinetic energy of a fluid. Conventionally, electric power has been generated from kinetic energy of a fluid.
For example, in a typical wind electric generating facility, a propeller receives wind and thereby rotates. The rotary shaft of the propeller is connected to the input shaft of a power generator, and along with the rotation of the propeller, the input shaft of the power generator rotates. Thereby, electric power is generated in the power generator. In short, in a typical wind electric generating facility, wind energy is converted to kinetic energy of the rotary shaft of a propeller, and the kinetic energy of the rotary shaft is converted to electric energy.
Japanese Patent Application Publication No. 2011-89492 (Patent Literature 1) suggests a wind electric generating facility with improved energy use efficiency. The electric generating facility disclosed in Patent Literature 1 includes a heat generator (retarder 30 in Patent Literature 1) that generates thermal energy in the process of converting wind energy to electric energy.
In the wind electric generating facility disclosed in Patent Literature 1, wind energy is converted to kinetic energy of the rotary shaft of a propeller, and the kinetic energy of the propeller is converted to hydraulic energy of a hydraulic pump. The hydraulic energy rotates a hydraulic motor. The spindle of the hydraulic motor is connected to the rotary shaft of the heat generator, and the rotary shaft of the heat generator is connected to the input shaft of a power generator. Along with rotation of the hydraulic motor, the rotary shaft of the heat generator rotates, and the input shaft of the power generator rotates, whereby electricity is generated in the power generator.
The heat generator utilizes eddy currents generated by the effects of magnetic fields from permanent magnets to reduce the rotational speed of the rotary shaft of the heat generator. Accordingly, the rotational speed of the spindle of the hydraulic motor is reduced, and the rotational speed of the propeller is adjusted via the hydraulic pump.
In the heat generator, the generation of eddy currents leads to generation of braking force to reduce the rotational speed of the rotary shaft of the heat generator, and generation of heat as well. Thus, a part of wind energy is converted to thermal energy. According to Patent Literature 1, the heat (thermal energy) is collected in a heat storage device, and the motor is driven by the collected thermal energy, whereby the power generator is driven. Consequently, electricity is generated in the power generator.